1. Clinical Overview
Flavoxate hydrochloride is a urinary antispasmodic agent used primarily for the symptomatic relief of dysuria, urgency, nocturia, suprapubic pain, frequency, and incontinence associated with various urological conditions. It acts as a direct smooth muscle relaxant with anticholinergic properties, specifically targeting the lower urinary tract. In the Indian context, it is a widely prescribed first-line therapy for overactive bladder (OAB) symptoms and bladder spasms.
| Onset | Duration | Bioavailability |
|---|---|---|
| Approximately 55-60 minutes after oral administration. | Approximately 4-6 hours. | Approximately 90-95%. |
2. Mechanism of Action
Flavoxate exerts its therapeutic effect through a dual mechanism: 1) Direct smooth muscle relaxation of the detrusor muscle in the urinary bladder, independent of muscarinic blockade. 2) Competitive antagonism of muscarinic acetylcholine receptors (primarily M1 and M3 subtypes) in the bladder, reducing involuntary contractions. This combined action increases bladder capacity, delays the initial desire to void, and reduces the frequency of uninhibited contractions.
3. Indications & Uses
- Symptomatic relief of dysuria, urgency, frequency, and incontinence associated with cystitis, prostatitis, urethritis, and urethrocystitis/urethrotrigonitis.
- Management of symptoms of overactive bladder (OAB) with urge incontinence.
- Post-operative bladder spasm following urological procedures (e.g., TURP, catheterization).
4. Dosage & Administration
Adult Dosage: 200 mg orally three to four times daily. The usual recommended dose is one 200 mg tablet 3-4 times a day.
Administration: Tablet should be swallowed whole with a full glass of water, with or without food. If gastrointestinal upset occurs, administer with food. Do not crush or chew. Maintain adequate fluid intake unless contraindicated.
5. Side Effects
Common side effects may include:
- Dry mouth (xerostomia)
- Nausea
- Vomiting
- Blurred vision (mydriasis)
- Dry eyes
- Constipation
- Drowsiness/sedation
- Headache
- Dizziness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Anticholinergics (e.g., Oxybutynin, Tolterodine, Atropine, TCAs) | Additive anticholinergic side effects (dry mouth, constipation, urinary retention, blurred vision, tachycardia). | Major |
| Potassium Chloride (wax-matrix tablets) | Increased risk of gastrointestinal lesions; flavoxate may delay GI transit. | Moderate |
| CNS Depressants (e.g., Alcohol, Benzodiazepines, Opioids) | Enhanced sedative effects, increased drowsiness and dizziness. | Moderate |
| Metoclopramide | Antagonizes the prokinetic effect of metoclopramide on GI motility. | Moderate |
| Digoxin | Theoretical risk of increased digoxin absorption due to reduced GI motility; monitor digoxin levels. | Minor |
7. Patient Counselling
- DO take the tablet as prescribed, usually 3-4 times a day.
- DO swallow the tablet whole with a full glass of water.
- DO inform your doctor if you have glaucoma, prostate problems, or heart disease.
- DO maintain adequate fluid intake unless advised otherwise.
- DONT crush, chew, or break the tablet.
- DONT drive or operate heavy machinery if you feel dizzy or drowsy.
- DONT take alcohol while on this medication.
- DONT stop the medication abruptly without consulting your doctor.
8. Toxicology & Storage
Overdose: Symptoms are primarily an extension of its anticholinergic effects: severe dry mouth, blurred vision, dilated pupils (mydriasis), tachycardia, palpitations, hyperthermia, urinary retention, constipation, ileus, CNS effects (restlessness, confusion, hallucinations, delirium, seizures, respiratory depression, coma).
Storage: Store below 30°C, in a cool, dry place, protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.